Functional Anatomy and Biomechanics of Shoulder Stability in the Athlete

doi:10.1016/j.csm.2013.07.001

Clinics in Sports Medicine

Volume 32, Issue 4, October 2013, Pages 607-624

https://doi.org/10.1016/j.csm.2013.07.001 Get rights and content

Section snippets

Key points

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The large range of motion afforded by the glenohumeral joint results in a propensity for instability.
•
The constitutional trait of laxity facilitates extensive motion in multiple planes and may be essential to athletic performance.
•
Range of motion and joint distractibility are increased in hyperlaxity, which is considered as instability when associated with loss of function.
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Strength and stability of the joint are highly dependent on both static and dynamic restraints.
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Soft tissue lesions associated

What is instability?

The constitutional trait of hyperlaxity and the pathologic condition of instability represent distinct clinical entities.¹ Laxity is the asymptomatic passive translation of the humeral head on the glenoid and may be essential to athletic performance. In hyperlaxity, this range of joint motion and joint distractibility are increased without loss of function. Glenohumeral instability is defined as excessive translation of the humeral head on the glenoid associated with a functional deficit.¹

Normal shoulder stability

The balance between stability and mobility within the shoulder is achieved through complex interactions involving static and dynamic restraints.¹ The bony static stabilizers include the glenoid, humeral head, and proximal humerus. The soft tissue passive stabilizers include the glenoid labrum, negative intra-articular pressure, articular cartilage surface, the glenohumeral ligaments, and the glenohumeral joint capsule. Soft tissue dynamic stabilizers are tendon-muscle complexes that provide

Classification of shoulder instability

The cause of shoulder instability is complex and multifactorial, and although several classification systems have been suggested, there is no all-encompassing system that adequately serves as a guide to treatment, predicts outcome, or facilitates communication between clinicians. Instability has been described in terms of direction (anterior, posterior, inferior, or multidirectional), degree of instability (dislocation, subluxation, or microinstability), chronology (acute, chronic, or acute on

Pathogenesis of instability in the athlete

Three broad etiologic categories have been implicated in instability of the shoulder: repetitive microtrauma to the shoulder, acute traumatic events, and purely atraumatic causes. It is crucial to identify the correct pathogenesis of instability so that treatment can be appropriately tailored to the patient’s needs.

Pathoanatomy of traumatic anterior instability

Traumatic anterior shoulder instability in the athlete usually occurs with a posteriorly directed force applied to the anterior aspect of an abducted, externally rotated arm. A direct blow (from posterior) can also cause a traumatic anterior dislocation. The humeral head is driven forward, producing a spectrum of soft tissue and bony lesions that are implicated in the pathogenesis of recurrent instability.

Pathoanatomy of traumatic posterior instability

The most frequent cause of recurrent posterior shoulder instability in the athlete is repetitive microtrauma to the posterior shoulder complex. In contrast to anterior instability, acute dislocation is usually not the most common initial presentation of posterior instability.⁵⁰ A spectrum of soft tissue and bony pathologies is encountered, the nature of which depends on the cause of the instability.

Pathoanatomy of atraumatic instability

It is challenging to define atraumatic instability because activities of daily living and improper shoulder mechanics may lead to damage at a molecular level. Many athletes with evidence of constitutional ligamentous laxity develop unilateral instability only after a discrete injury; whilst some degree of inherited predisposition to traumatic instability is implied by its occurrence bilaterally in a quarter of patients.⁷³ Atraumatic instability includes the diagnosis of multidirectional

Summary

Glenohumeral joint motion results from a complex interplay between static and dynamic stabilizers that require intricate balance and synchronicity. Instability of the shoulder is a commonly encountered problem in active populations, especially young athletes. The underlying pathoanatomy predisposing to further episodes and the needs of individual athletes must be considered in determining the most appropriate treatment.

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References (75)

P.E. Huysmans et al.
The shape of the inferior part of the glenoid: a cadaveric study
J Shoulder Elbow Surg
(2006)
R.S. Churchill et al.
Glenoid size, inclination, and version: an anatomic study
J Shoulder Elbow Surg
(2001)
S.B. Lippitt et al.
In vivo quantification of the laxity of normal and unstable glenohumeral joints
J Shoulder Elbow Surg
(1994)
B. Jost et al.
Anatomy and functional aspects of the rotator interval
J Shoulder Elbow Surg
(2000)
N.M. Digiovine et al.
An electromyographic analysis of the upper extremity in pitching
J Shoulder Elbow Surg
(1992)
E.M. Wolf et al.
Humeral avulsion of glenohumeral ligaments as a cause of anterior shoulder instability
Arthroscopy
(1995)
T.J. Neviaser
The anterior labroligamentous periosteal sleeve avulsion lesion: a cause of anterior instability of the shoulder
Arthroscopy
(1993)
S.H. Treacy et al.
Rotator interval capsule closure: an arthroscopic technique
Arthroscopy
(1997)
S.M. Lephart et al.
Proprioception of the shoulder joint in healthy, unstable, and surgically repaired shoulders
J Shoulder Elbow Surg
(1994)
J.E. Tibone et al.
Evaluation of a proprioception pathway in patients with stable and unstable shoulders with somatosensory cortical evoked potentials
J Shoulder Elbow Surg
(1997)

N. Yamamoto et al.

Contact between the glenoid and the humeral head in abduction, external rotation, and horizontal extension: a new concept of glenoid track

J Shoulder Elbow Surg

(2007)

S.S. Burkhart et al.

Traumatic glenohumeral bone defects and their relationship to failure of arthroscopic Bankart repairs: significance of the inverted-pear glenoid and the humeral engaging Hill-Sachs lesion

Arthroscopy

(2000)

S.H. Kim et al.

Kim's lesion: an incomplete and concealed avulsion of the posteroinferior labrum in posterior or multidirectional posteroinferior instability of the shoulder

Arthroscopy

(2004)

E. Schwartz et al.

Posterior shoulder instability

Orthop Clin North Am

(1987)

W.C. Doukas et al.

Anatomy, pathophysiology, and biomechanics of shoulder instability

Orthop Clin North Am

(2001)

I.R. Murray et al.

Traumatic anterior shoulder instability in the athlete

Scand J Med Sci Sports

(2013)

S.M. Johnson et al.

Shoulder instability in patients with joint hyperlaxity

J Bone Joint Surg Am

(2010)

E. Codman

The shoulder

(1934)

A.K. Saha

Dynamic stability of the glenohumeral joint

Acta Orthop Scand

(1971)

T. Lee

Clinical anatomy and biomechanics of the glenohumeral joint (including stabilizers)

C. Gerber et al.

Effect of selective capsulorrhaphy on the passive range of motion of the glenohumeral joint

J Bone Joint Surg Am

(2003)

A.C. Burkart et al.

Anatomy and function of the glenohumeral ligaments in anterior shoulder instability

Clin Orthop Relat Res

(2002)

L.A. Curl et al.

Glenohumeral joint stability. Selective cutting studies on the static capsular restraints

Clin Orthop Relat Res

(1996)

S.M. Howell et al.

The glenoid-labral socket. A constrained articular surface

Clin Orthop Relat Res

(1989)

A.M. Halder et al.

Effects of the glenoid labrum and glenohumeral abduction on stability of the shoulder joint through concavity-compression: an in vitro study

J Bone Joint Surg Am

(2001)

S.J. Miller

Shoulder anatomy and biomechanics

J.E. Labriola et al.

Stability and instability of the glenohumeral joint: the role of shoulder muscles

J Shoulder Elbow Surg

(2005)

T. Mihata et al.

Effect of rotator cuff muscle imbalance on forceful internal impingement and peel-back of the superior labrum: a cadaveric study

Am J Sports Med

(2009)

L.N. Sciaroni et al.

Open surgical repair restores joint forces that resist glenohumeral dislocation

Clin Orthop Relat Res

(2002)

C. Gerber et al.

Classification of glenohumeral joint instability

Clin Orthop Relat Res

(2002)

A. Allen

Clinical evaluation of the unstable shoulder

S.C. Thomas et al.

An approach to the repair of avulsion of the glenohumeral ligaments in the management of traumatic anterior glenohumeral instability

J Bone Joint Surg Am

(1989)

P.A. Dowdy et al.

Shoulder instability. An analysis of family history

J Bone Joint Surg Br

(1993)

J.E. Kuhn

A new classification system for shoulder instability

Br J Sports Med

(2010)

C.R. Rowe et al.

Voluntary dislocation of the shoulder. A preliminary report on a clinical, electromyographic, and psychiatric study of twenty-six patients

J Bone Joint Surg Am

(1973)

A. Lewis et al.

Mini symposium: shoulder instability (ii). The classification of shoulder instability: new light through old windows!

Curr Orthop

(2004)

A. Jaggi et al.

Rehabilitation for shoulder instability

Br J Sports Med

(2010)

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Despite the extensive literature on anterior glenohumeral instability, to date, there are no studies that report on the quality of life following a Latarjet-Bristow procedure with recurrent anterior shoulder instability. The purpose of this study was to evaluate the quality of life in patients who had a Latarjet-Bristow procedure.
A single-center retrospective review with a prospective recall of patients who underwent a Latarjet-Bristow technique for recurrent anterior glenohumeral instability between January 2017 and March 2020. Outcomes measures included health-related quality of life using the Short Form-36 (SF-36) questionnaire and patient-related outcome measures using the Western Ontario Shoulder Instability Index and Rowe scores.
A total of 66 patients were identified to participate in the study; 40 (60.6%) responded and were included in the analysis. There were nine females and 31 males, with a median age of 32 years (27.5‒41 years). Three cases had bilateral anterior shoulder instability with a single joint being operated and three patients were epileptic. Physical and mental components summary of the SF-36 showed a better health-related quality of life in the general population. There was a significant strong correlation between SF-36 and Western Ontario Shoulder Instability Index. However, SF-36 and Rowe score showed a fair correlation.
The Latarjet-Bristow procedure improves the quality of life in a general population similarly to an athletic population. The number of episodes of dislocation before surgery and the delayed surgical intervention did not increase the recurrent anterior shoulder instability rates postoperatively.
Postoperative MRI of Shoulder Instability
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Although first time acute dislocation occurs usually as the result of a significant traumatic event, such as a fall on an outstretched arm with the arm in abduction and external rotation, recurrent multiple shoulder dislocations can recur following more minor traumatic events. This in part is owing to chronic shoulder joint laxity and instability resulting from repetitive and chronic injury to the static and/or dynamic joint stabilizers or osseous injuries to the glenohumeral joint.2–4 Surgical treatment options for shoulder instability and postoperative outcomes depend on the accurate preoperative assessment of the patient, including the correct imaging characterization of the glenoid and humeral bone injuries.5–8
Humeral elevation reduces the dynamic control ratio of the shoulder muscles during internal rotation
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The stability of the shoulder joint complex is largely dependent on dynamic contraction of the rotator cuff muscles.1–3 It has been suggested that changes in dynamic shoulder stability can contribute to shoulder injuries and pathologies such as shoulder impingement or instability.2–4 Pain in the shoulder region and accompanying impaired dynamic stability of the shoulder joint complex are typically noticeable during elevation of the upper arm and overhead activities such as tennis and volleyball serves when rotation of the humerus at the glenohumeral joint (GHJ) occurs.
To determine the differences in the dynamic control ratio of the glenohumeral joint rotators, during internal rotation at 20° and 60° of humeral elevation in the scapular plan. Dynamic control ratio (DCR) is defined as the ratio between eccentric action of the lateral rotators and the concentric action of the medial rotators.
A cross-sectional laboratory study.
Thirty asymptomatic participants (men n = 14, women n = 16, mean age = 29.4 ± 8.9 years, BMI: 24.1 ± 5.4) were tested. Peak torque generated by the concentric action of the MR and the eccentric action of the LR of the shoulder joint and the DCR were evaluated on the dominant arm using an isokinetic dynamometer at 20° and 60° of humeral elevation at a speed of 20°/s.
There was a significant decrease in the DCR at 60° humeral elevation when compared to 20° humeral elevation (p < 0.05). This decrease was due to the significant decrease in eccentric peak torques at 60° humeral elevation when compared to 20° (p < 0.05). However, there was no significant difference in the concentric peak torques between 20° and 60° (p > 0.05).
The significant decrease in the DCR as a consequence of a decrease in the eccentric peak torque of the LR when the humerus is in a more elevated position suggests that the introduction of humeral elevation can be used as a progression for improving the eccentric action of the shoulder LR and subsequently the dynamic control of the shoulder.
Concurrent validity of handheld dynamometer measurements for scapular protraction strength
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The shoulder is considered an unstable joint due to its anatomical features associated with a wide range of motion.1,2
Handheld dynamometers (HHD) provide quick and low-cost assessments of muscle strength and their use has been increasing in clinical practice. There is no available data related to the validity of HHD for this measurement.
To verify the concurrent validity of scapular protraction measurements using an HHD.
Individuals with traumatic anterior glenohumeral instability were allocated in Instability Group (n = 20), healthy swimmers were allocated in Athletes Group (n = 19) and healthy subjects were allocated in Sedentary Group (n = 21). Concurrent validity was verified by the Pearson correlation test between HHD and isokinetic measurements. The agreement between instruments was verified by Bland–Altman plots, for each of the two HHD positions.
A moderate correlation was observed between seated (r = 0.59) and lying supine HHD (r = 0.54) and isokinetic dynamometer measurements for the all groups. Separated group analysis exhibited a strong correlation between seated HHD and isokinetic dynamometer measurements in the Instability Group (r = 0.80), Sedentary Group (r = 0.79) and Athletes Group (r = 0.76). The Bland–Altman plot showed greater agreement in the seated position than the lying supine position when comparing measurements with the HHD and isokinetic in both the general sample and separated groups.
The HHD may be considered a valid tool for assessing scapular protraction muscle strength among healthy athletes, non-athletes and subjects with shoulder instability. We recommend to assess subjects in the seated position and to be aware that the HHD tends to overestimate the peak force, compared with the gold-standard isokinetic dynamometer.
Isokinetic shoulder strength and its associations to injury in tactical populations: A critical review
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